Various types of pressure relief valves are known for controlling fuel delivery pressure in so-called single-line forward fuel injection systems. Diaphragm-type pressure regulating valves have been used but are large and expensive. Smaller and less expensive ball-on-seat valves have also been used but are not sufficiently sensitive to changes in the fuel consumption rate of the motor for application as a pressure regulating valve in single line forward motor vehicle injection systems.
A prior art pressure regulating valve is seen in U.S. Pat. No. 5,762,101 issued to General Motors Corporation, the entire disclosure of which is incorporated herein by reference. The valve of the '101 patent includes a valve element having a surface which is spring biased to close against a circular valve seat. An annular orifice is created when the flow overcomes the bias of the spring and moves the valve element away from the valve seat. The flow directing surface of the valve element redirects fluid flow upstream of the orifice. The fluid is redirected at an included angle less than 180° to induce on the valve element a force reaction, which cooperates with a fluid pressure force reaction on the valve element to improve sensitivity of the valve element to changes in fluid pressure upstream of the annular flow orifice, attributable to changes in the rate of fuel consumption by the motor. A skirt of the flow directing surface downstream of the annular flow orifice directs fluid flow substantially parallel to the direction of movement of the valve element to minimize the sensitivity of the valve element to a velocity-induced pressure gradient across the valve element. While the valve of the '101 patent improves the sensitivity response to fuel consumption at the motor, a reliable seal between the concave hemispherical valve element and truncated valve seat is sometimes difficult to achieve. It would therefore be desirable to have an improved pressure relief valve which is sensitive to fuel consumption at the motor and reliably maintains a seal in the closed position of the valve even in the event of non-axial movement of the valve element, for example.